S-NRLF 


am 


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American  Society  of  Municipal 
Improvements,  1915 


HOB 


SPECIFICATIONS  FOR 


BITUMINOUS  PAVING 

ADOPTED  OCTOBER  14,  1915 


These  specifications  will  be  modified  from  time  to  time 
to  keep  them  fully  up  to  date.     Suggestions  as  to 
modifications    or    additions   are    solicited   and 
should  be  sent  to  the  Secretary,  or  to  Linn 
White,  South  Park  Commission,  Chi- 
cago, 111.,  Chairman  of  the  Sub- 
Committee  on   Specifications 
for   Bituminous  'Paving, 


GEORGE      W.     TILLSON 

Boro  Hall,  Brooklyn,  New  York 
Chairman  of  General  Committee  on  Standard  Specifications 


COPYRIGHTED,  1916 

Any  municipality  which  is  represented  in  the  membership  of  the  S  jciety  by  one  or  more 
city  officials,  will  be  given  free  permission  to  use  these  specifications  or  any 
part  of  them  upon  application  to  the  Secretary 


PUBLISHED  BY  THE  SOCIETY 
CHARLES  CARROLL  BROWN,  Secretary 

702  WULSIN  BUILDING 
INDIANAPOLIS,   INDIANA 


0 


SPECIFICATIONS  FOR  BITUMINOUS  CONCRETE 
PAVEMENT. 

Sub-Grade. 

The  contractor  will  be  required  to  do  all  of  the  grading  necessary 
to  bring  the  surface  to  the  proper  sub-grade  as  determined  by  the 
lines  and  grades  given  by  the  engineer.  If  the  material  at  sub-grade 
is  of  an  unstable  character  and  unfit  for  foundation,  the  contractor 
shall  make  such  additional  excavation  as  may  be  determined  by  the 
engineer  and  refilled  with  approved  material.  After  all  necessary 
grading  has  been  done  to  bring  this  surface  to  sub-grade,  the  street 
shall  be  thoroly  rolled  with  an  approved  road  roller  weighing 
not  less  than  ten  tons.  If  settlement  occurs  the  depressions  shall 
be  filled  and  then  re-rolled  until  the  surface  is  solid,  uniform  and 
parallel  with  the  grade  and  cross-section  of  the  finished  pavement. 
All  filling  shall  be  free  from  animal  or  vegetable  matter  and  of  a 
character  approved  by  the  engineer.  In  cases  of  spongy  or  yielding 
sub-grade  some  other  means  besides  ordinary  rolling  and  sprinkling 
must  be  employed  to  obtain  satisfactory  compaction  of  the  sub-grade. 
In  the  case  of  loose,  sandy  soils,  a  small  amount  of  cinders,  gravel 
or  fine  crushed  stone  spread  over  the  surface  will  often  put  it  in  a 
condition  to  be  compacted  under  the  roller.  In  the  case  of  clay 
soils  that  puddle  up  and  wave  or  creep  under  continued  rolling,  it  is 
best  to  roll  as  dry  as  possible  and  to  be  sparing  in  the  use  of  water 
when  rolling  the  first  layer  of  macadam.  Cinders,  gravel  or  stone 
screenings  will  often  help  in  rolling  such  sub-grades. 

Sub-Drainage. 

When  the  soil  is  of  such  a  character  that  it  retains  an  excessive 
amount  of  moisture,  such  as  clay,  subject  to  swelling  or  heaving 
under  the  action  of  frost,  or  sands  similar  to  quicksand  that  do  not 
afford  a  ready  natural  drainage,  sub-drains  should  be  provided. 

These  may  be  of  two  general  kinds;  first,  tile  drains  of  open  por- 
ous material  of  vitrified  tile  laid  with  open  joints;  second,  trenches 
filled  with  broken  stone,  gravel,  cinders  or  other  similar  material. 

In  some  cases  it  may  be  sufficient  to  construct  a  sub-drain  on  each 
side  of  the  roadway  at  or  near  the  lines  of  the  gutters,  but  when  the 


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soil  is  of  a  very  wet  nature  it  may  be  advisable  to  lay  additional  lines 
of  drains  which  may  be  in  or  near  the  middle  of  the  roadway.  This 
system  of  drains  may  be  varied  by  diagonal  lines  of  drains  running 
from  near  the  crown  of  the  roadway  to  the  gutters. 

In  all  cases  the  drains  should  have  connections  with  the  existing 
sewers,  catch  basins  or  inlets. 

New  Macadam  Foundation. 

If  the  pavement  is  to  be  laid  on  a  new  macadam  foundation  or 
base,  the  latter  shall  be  built  as  follows: 

The  total  thickness  of  the  macadam  base  will  vary  according  to 
character  of  soil,  drainage,  kind  of  stone  available,  etc.  In  general, 
the  macadam  base  should  be  constructed  of  broken  stone  which  is 
sound,  hard  and  durable  under  traffic.  The  broken  stone  should 
be  separated  into  different  sizes  by  screening,  the  smaller  sizes  with 
the  dust,  being  used  to  fill  and  bond  together  the  larger  sizes.  The 
thickness  of  the  base  should  be  regulated  by  experience  in  construct- 
ing ordinary  water-bound  macadam  roads  in  similar  situations,  the 
total  thickness  of  pavement,  including  wearing  surface,  being  made 
the  same  or  a  little  less  than  well  constructed  macadam. 

After  the  sub-grade  has  been  carefully  prepared,  spread  a  layer  of 
clean  stone  passing  a  three  (3')  to  three  and  one-half  (3^)  inch 
revolving  screen  and  held  on  a  two  (2)  inch  screen  to  a  depth  suffi- 
cient when  thoroly  rolled  to  form  about  two-thirds  (2/3)  of  the 
total  thickness  of  the  base.  The  thickness  of  this  layer  should  be 
regulated  by  laying  on  the  sub-grade  at  proper  intervals,  cubical 
blocks  of  wood  of  the  proper  dimensions  to  give  the  desired  thick- 
ness. Over  this  layer  of  stone,  spread  with  shovels  stone  screenings 
in  sufficient  quantity  to  fill  the  voids  between  the  larger  stone.  The 
screenings  should  be  spread  gradually  and  thoroly  rolled  with  a  road 
roller  weighing  at  least  10  tons  during  the  process  of  spreading  the 
screenings.  As  the  screenings  are  worked  into  the  coarse  stone 
under  the  roller,  more  should  be  added  here  and  there  where  voids 
appear.  At  first  the  rolling  should  be  done  dry  until  the  stone  appears 
to  be  well  filled,  then  the  surface  should  be  well  sprinkled  and  again 
rolled,  the  rolling  and  sprinkling  continued  until  the  layer  of  stone 
is  thoroly  compacted  and  no  more  screenings  can  be  forced  in.  Just 
enough  screenings  shall  be  used  to  fill  and  bond  the  stone  leaving 
no  surplus  screenings  on  the  top. 


The  above  method  may  be  varied  by  using  the  crusher  run  of  stone 
without  the  addition  of  any  other  filler  where  the  small  sizes  are 
not  in  excess.  Also  a  filler  other  than  stone  screenings,  such  as 
bank  gravel  or  sand,  may  be  used  in  some  cases  where  experience 
with  materials  available  shows  better  results  can  be  obtained.  Under 
some  conditions  the  character  of  soil  and  stone  available  may  be 
such  as  not  to  require  the  use  of  any  filler  with  the  stone  of  the 
first  course.  The  specifications  given,  however,  represent  the  best 
average  practice  where  stone  with  bonding  value,  such  as  limestone 
or  trap  rock,  can  be  obtained. 

When  the  first  layer  of  macadam  is  completed  as  specified,  spread 
a  second  layer  of  clean  stone  passing  a  two  (2)  or  two  and  one-half 
(2l/2)  inch  screen  and  held  on  a  one  (1)  inch  screen  to  a  depth 
sufficient  when  thoroly  rolled  to  form  the  remaining  one  third  •  of 
the  total  thickness  of  the  base.  Over  this  layer  of  stone  spread 
evenly  with  shovels  stone  screenings  and  roll  with  the  application 
of  water  by  sprinkling.  The  sprinkling  and  rolling  shall  be  con- 
tinued until  the  stone  is  well  bonded  and  until  no  more  compres- 
sion can  be  observed  under  the  roller.  Just  enough  filler  should  be 
used  to  accomplish  this  purpose  and  not  enough  to  form  a  layer  or 
film  over  the  surface  of  the  stone.  It  is  better  not  to  fill  the  stone 
quite  flush,  leaving  the  coarse  particles  of  stone  slightly  projecting, 
so  as  to  have  a  coarse,  grainy  base  upon  which  to  put  the  wearing 
surface. 

As  an  alternate  method  of  construction  the  macadam  may  be 
well  filled  with  screenings,  watered  and  rolled  until  flush  up  smooth. 
Over  the  surface  of  the  macadam  base  thus  constructed  shall  be 
spread  a  layer  of  clean  stone  of  a  size  to  pass  a  two  (2)  inch  ring 
and  be  retained  on  a  one  (1)  inch  ring.  This  layer  of  stone  shall 
average  one  and  one-half  (I1/*)  inches  or  practically  only  one  stone 
deep  and  is  for  the  purpose  of  forming  a  binder  or  key  between  the 
base  and  wearing  surface  and  thus  preventing  lateral  displacement 
of  the  surface.  After  being  spread  evenly  it  shall  be  lightly  rolled 
only  enough  to  partially  imbed  the  stone  and  set  them  firmly  in 
place  without  crushing  or  forcing  the  fine  material  up  from  below 
to  fill  the  surface  voids.  The  final  rolling  should  be  done  while 
the  macadam  base  is  still  moist  and  comparatively  soft. 

The  thickness  of  the  pavement,  including  base  and  wearing  sur- 
face, should  vary  according  to  local  conditions  and  should  be  fixed 


by  the  engineer  in  charge  when  all  the  varying  conditions  of  soil, 
drainage,  traffic  and  materials  of  construction  are  understood.  In 
general,  a  thickness  of  macadam  base  of  eight  (8)  inches  with  a 
wearing  surface  of  two  inches  will  be  enough  for  any  except  the 
most  adverse  conditions,  and  a  base  of  four  to  four  and  one-half 
(4y2)  inches  with  a  wearing  surface  of  from  one  and  one-half 
(1^2)  to  two  (2)  inches  will  meet  the  most  favorable  conditions 
of  firm,  unyielding  soils  and  light  traffic. 

Old  Macadam  Foundation. 

If  the  pavement  is  to  be  laid  on  an  old  macadam  foundation,  the 
surface  shall  be  thoroly  swept  and  cleaned  of  all  fine  material  that 
may  be  caked  upon  the  surface  of  the  stone  or  lying  loose  as  dust, 
thereby  exposing  the  clean,  coarse  stone  for  the  reception  of  the 
bituminous  concrete. 

If  the  old  macadam  does  not  present  the  desired  coarse,  grainy 
surface,  or  is  not  at  proper  and  satisfactory  grade  after  cleaning, 
it  shall  be  spiked  up  and  redressed  to  the  desired  crown  and  grade, 
the  coarse  stone  being  brought  to  the  top  by  harrowing  or  other- 
wise, or  new  stone  added  where  needed.  It  shall  then  be  watered 
and  rolled  until  thoroly  compacted.  If  the  result  is  not  the  re- 
quired coarse,  grainy  surface,  a  layer  of  clean  stone  shall  be  spread 
and  lightly  rolled  as  described  above  in  the  paragraph  relating  to 
new  macadam  foundation. 

Concrete  Foundation. 

When  a  portland  cement  concrete  foundation  is  used,  it  should 
be  laid  according  to  the  standard  specifications  adopted  for  con- 
crete foundation.  The  surface,  however,  should  be  roughened  to 
form  a  key  for  the  wearing  surface.  This  may  be  done  by  using 
coarse  stone  of  fairly  uniform  size  and  laying  the  concrete  fairly 
wet,  or  by  brooming,  washing  with  a  hose  before  hard  set,  tamp- 
ing with  grooved  rammers,  or  by  spreading  a  light  layer  of  coarse, 
clean  stone  over  the  fresh  concrete  and  lightly  tamping. 

Curb. 

If  a  curb  or  curb  and  gutter  is  used,  the  face  against  which  the 
paving  material  will  be  laid  shall  be  painted  with  a  coat  of  hot 
bituminous  cement  in  advance  of  the  pavement. 


A  curb  or  curb  and  gutter  should  be  used  in  all  cases  of  a  street 
devoted  to  miscellaneous  uses  and  where  there  is  occasion  for  many 
vehicles  to  stop  at  the  curb  line,  but  in  the  case  of  a  park  driveway 
or  a  suburban  highway,  a  bituminous  concrete  pavement  may  be 
successfully  used  without  a  curb.  No  other  protection  for  the  edge 
of  the  pavement  is  required  except  to  provide  a  coarse,  grainy  base 
into  which  the  paving  material  is  rolled. 

Wearing  Surface. 

On  the  foundation,  as  heretofore  specified,  shall  be  laid  the 
bituminous  concrete  wearing  surface,  which  shall  consist  of  a  min- 
eral aggregate  mixed  with  bituminous  cement  and  laid  as  herein- 
after specified. 

This  wearing  surface  shall  have  a  thickness  of  .  .  inches  after 
thoro  compression  with  a  roller. 

For  heavy  traffic  a  thickness  of  two  (2)  inches  is  sufficient  for 
all  practical  purposes  and  in  some  cases  will  afford  more  stability 
than  a  greater  thickness. 

For  moderate  and  light  traffic  one  and  one-half  (1^)  inches 
will  be  sufficient  thickness  for  the  wearing  surface  when  laid  on  a 
well  constructed  base  as  specified  above. 

Mineral  Aggregate. 

The  mineral  aggregate  shall  consist  of  a  mixture  of  broken  stone 
and  sand,  to  which  shall  be  added  as  required,  stone,  dust  or  port- 
land  cement. 

Any  sound,  durable  stone,  either  trap  rock,  limestone  or  granite, 
usually  considered  suitable  for  macadam,  may  be  used.  It  should 
be  broken  as  nearly  cubical  as  practicable.  It  should  not  show 
distinct  planes  of  cleavage  or  crystalline  faces  and  should  not  readily 
crush  or  split  under  the  roller  when  being  rolled  in  the  pavement. 
Between  two  kinds  of  stone,  choice  should  generally  be  made  of 
the  one  showing  the  greater  toughness  rather  than  hardness.  A 
certain  percentage  of  absorption,  such  as  is  shown  by  the  better 
grades  of  limestone,  is  a  desirable  quality,  as  the  bonding  strength 
of  the  cement  is  somewhat  improved  thereby. 

The  sand  shall  be  hard-grained,  moderately  sharp,  free  from 
loam  or  other  foreign  material  and  varying  in  size  from  that  passing 


a  one-quarter  (%)  inch  screen  to  dust  passing  a  two  hundred-mesh 
screen,  and  there  should  not  be  over  twenty  per  cent  held  on  the 
ten-mesh  screen. 

Dust  in  the  form  of  finely  ground  limestone  or  portland  cement 
may  be  added  to  the  mixture,  but  in  such  quantities  that  the  screen- 
ings of  the  total  ingredients  entering  into  the  mix  shall  in  no  case 
show  over  eleven  (11)  per  cent  by  weight  passing  a  200-mesh 
screen. 

The  proportions  of  the  various  ingredients  composing  the  Bitu- 
minous Concrete  shall  be  as  follows: 

Passing  200  Mesh  Screen,  7-10  per  cent. 

Passing  80  Mesh  Screen,  but  retained  on  a  200,   10-20  per  cent. 

Passing  40  Mesh  Screen,  but  retained  on  an  80,  10-25  per  cent. 

Passing  20  Mesh  Screen,  but  retained  on  a  40,   10-25  per  cent. 

Passing  8  Mesh  Screen,  but  retained  on  a  20,   10-20  per  cent. 

Passing  4  Mesh  Screen,  but  retained  on  an  8,   15-20  per  cent. 

Passing  2  Mesh  Screen,  but  retained  on  a  4,     5-10  per  cent. 

The  minimum  amount  of  bitumen  allowed  shall  only  be  used  in 
mixtures  containing  the  minimum  total  passing  the  80-mesh.  The 
percentage  of  bitumen  must  be  increased  above  the  minimum  as 
the  total  passing  the  80-mesh  increases. 

The  item  designated  as  Dust  includes  in  addition  to  the  portland 
cement  or  stone  dust  that  may  be  added,  fine  sand  passing  a  200- 
mesh  screen  not  exceeding  5  per  cent  of  the  total  mixture  and  such 
200-mesh  mineral  dust  self-contained  in  the  refined  asphalt. 

Method  of  Mixing. 

The  aggregate  shall  be  dried  and  heated  in  properly  designated 
driers  before  mixing  with  the  bituminous  cement.  Thd  driers  shall 
be  of  the  revolving  type,  thoroly  agitating  and  turning  the  materials 
during  the  process  of  drying.  When  the  aggregate  is  thoroly  dried 
and  heated  to  a  temperature  of  from  200  to  350  degrees  F.,  de- 
pending upon  the  bituminous  cement  used,  it  shall  be  immediately 
before  cooling  or  exposure  to  moisture,  mixed  with  the  hot  bitu- 
minous cement  as  hereinafter  specified.  If  stone  dust  is  used,  it  shall 
be  introduced  directly  into  the  mixer  without  passing  thru  the  drier. 

The  bituminous  cement  shall  be  melted  in  a  tank  arranged  so  the 
heat  can  be  properly  and  easily  controlled  and  regulated.  When 


melted  and  raised  to  a  temperature  of  from  200  to  350  degrees  F., 
depending  on  the  bituminous  cement  used,  it  shall  be  combined  in 
the  proper  proportions  with  the  hot  aggregate  and  immediately 
mixed  in  a  properly  designed  mixer  with  revolving  blades  until  a 
thoro  and  intimate  mixture  of  the  ingredients  has  been  accomplished 
and  the  particles  composing  the  aggregate  are  evenly  and  thoroly 
coated  with  the  bituminous  cement.  The  mixer  shall  not  be  exposed 
directly  to  the  action  of  fire. 

Method   of  Laying. 

While  still  hot  from  the  mixer,  the  paving  mixture  shall  be 
spread  evenly  on  the  foundation  with  hot  iron  rakes  and  shovels, 
so  that  when  compressed  writh  the  roller  it  shall  have  the  thickness 
specified,  with  the  surface  even  and  true  to  grade.  Along  the  curb 
and  around  manholes,  catch  basins  and  other  obstructions  in  the 
street,  where  the  roller  cannot  reach,  the  compression  shall  be 
secured  by  the  use  of  hot  iron  tampers.  The  rolling  and  tamping 
shall  be  done  as  quickly  as  possible  after  the  material  is  spread, 
while  still  hot  and  pliable.  When  the  paving  mixture  is  hauled 
on  the  street  in  dump  wagons  it  shall  be,  when  ordered  by  the 
engineer,  kept  covered  with  canvas  to  retain  heat,  dumped  on  plat- 
forms and  shoveled  into  place  and  raked  to  the  proper  grade.  As 
soon  as  spread  the  paving  mixture  shall  be  rolled  with  a  tandem 
roller  weighing  at  least  six  (6)  tons  and  the  rolling  continued, 
working  lengthwise  and  diagonally  of  the  street.  When  practicable, 
additional  compression  in  the  wearing  surface  should  be  secured  by 
the  use  of  a  ten-ton  roller.  Rolling  must  be  steadily  kept  up  and 
continued  until  all  roller  marks  shall  disappear  and  the  surface 
gives  indications  of  no  further  compressibility. 

The  paving  shall  be  done  continuously,  so  the  number  of  joints 
between  the  hot  and  cold  material  may  be  reduced  to  the  minimum. 
When  it  is  not  practicable  to  lay  it  continuously  and  a  joint  is 
unavoidable,  the  edge  of  the  cold  material  shall  be  trimmed  down 
to  a  rough  feather  edge,  and  the  surface,  where  the  joint  is  to 
be  made,  painted  over  with  bituminous  cement,  the  hot  material 
raked  over  the  feathered  edge  and  thoroly  rolled.  Instead  of  trim- 
ming the  cold  material,  joint  strips  may  be  used  consisting  of  strips 
of  canvas  about  eighteen  (18)  inches  wide  with  three  parallel  lines 
of  three-quarter  (^4)  inch  ropes  sewed  on  the  under  side  about 
three  (3)  inches  apart.  The  joint  strips  shall  be  laid  on  the  feather 


edge  of  the  freshly  raked  material  with  the  upper  rope  at  the  line 
where  the  thickness  begins  to  decrease  and  the  rolling  completed 
on  top  of  the  canvas  as  for  finished  pavement.  The  faces  of  the 
curb  and  gutter,  iron  castings,  etc.,  shall  be  painted  with  bituminous 
cement  before  the  paving  mixture  is  laid. 

Surface  Finish. 

As  soon  as  possible  after  the  rolling  of  the  mixture  is  finished, 
and  while  the  surface  is  still  fresh  and  clean,  and,  if  possible,  while 
warm,  a  seal  coat  of  bituminous  cement  of  prdperly  consistency  to 
be  flexible  when  cold  shall  be  spread  over  the  surface.  It  shall  be 
applied  while  at  a  temperature  of  from  200  degrees  to  350  degrees 
F.,  depending  upon  the  bituminous  cement  used,  and  evenly  spread 
with  rubber  squeegees  or  mops.  Only  a  sufficient  coat  shall  be 
spread  to  flush  the  surface  voids  without  leaving  an  excess.  Imme- 
diately over  this,  a  top  dressing  of  torpedo  sand,  fine  gravel  or  stone 
chips  free  from  dust,  which  must  be  thoroly  dry  and  heated  in  cold 
weather,  shall  be  spread  and  thoroly  rolled  into  the  surface.  A 
small  surplus  shall  be  left  to  be  worn  in  or  worn  away  by  the 
traffic. 

In  the  case  of  park  drives  and  roadways  not  subjected  to  heavy, 
constant  traffic,  and  where  a  more  grainy  and  coarse  surface  is 
desired,  the  surface  finish  specified  above  may  be  omitted  and  the 
following  method  of  finishing  adopted: 

As  the  bituminous  concrete  is  raked  to  grade,  and  just  before  the 
roller  comes  on  it,  spread  dry  stone  chips  or  coarse  torpedo  sand, 
evenly  with  swinging  motions  of  a  shovel,  until  the  surface  is  barely 
covered.  Then  roll  thoroly  as  specified  in  the  preceding  paragraph 
relating  to  method  of  laying.  If  bare  spots  appear  under  the  roller, 
sprinkle  more  chips  or  sand  and  continue  the  rolling  until  the  whole 
surface  is  fairly  covered. 

After  the  sand  or  stone  chips  have  worn  into  the  surface  the 
street  shall  be  swept,  all  excess  of  surfacing  material  removed  and 
the  street  left  clean. 

Asphaltic  Cement. 

The  asphaltic  cement  may  be  prepared  from  the  following  as- 
phalts combined  with  flux  as  hereinafter  specified,  if  flux  is  neces- 
sary: (1)  From  refined  natural  asphalt;  (2)  from  the  residue 

8 


obtained  in  the  careful  distillation  either  with  or  without  oxidation 
of  asphaltic  or  semi-asphaltic  petroleum;  (3)  from  any  uniform 
combination  of  the  preceding  materials  together  with  a  suitable  flux, 
if  flux  be  necessary,  such  combination  being  subject  to  the  approval 
of  the  engineer. 

Each  bidder  must  state  the  nature  and  origin  of  the  bitumen  to 
be  used  by  him  and  further,  shall  submit  samples  of  the  bituminous 
cement  with  his  proposal. 

The  asphaltic  cement  shall  pass  the  requirements  designated 
below : 

(1)  It  shall  have  a  penetration  of  from  40  to  85  at  77  degrees 
F.,  depending  upon  the  traffic  and  climatic  conditions  and  hardness 
of  the  pavement  desired.     A  penetration  of  from  40  to  50  in  most 
cements   will   produce    a   hard,    exceedingly   stable   pavement   which 
should  be  used  on  streets  subjected  to  constant  or  heavy  traffic. 

A  penetration  of  from  50  to  65  in  most  cements  will  produce  a 
pavement  best  calculated  to  meet  general  traffic  conditions.  The 
above  penetrations  are  measured  in  hundredths  centimeters  with  a 
No.  2  needle  weighted  with  one  hundred  grams  acting  for  five  (5) 
seconds. 

(2)  When  50  grams  of  the  cement  are  maintained  at  a  temper- 
ature of  325  degrees  F.,  for  five  hours  in  a  tin  box  2%  inches  in 
diameter   by    1^4    inches   deep,   there   must   not   be   volatilization   of 
more  than  5  per  cent  by  weight  of  the  bitumen  present,  nor  shall 
the  original  penetration  be  reduced  thereby  over  one-half. 

The  method  of  test  employed  is  that  recommended  by  the  Com- 
mittee on  Coal  Analysis  of  the  American  Chemical  Society. 

(3)  Of  the  bitumen  of  the  asphaltic  cement  which  is  soluble  in 
carbon   disulphide,   98^   per  cent  shall  be  soluble   in  carbon   tetra- 
chloride.     In  this  test  for  carbenes,  the  asphaltic  cement  to  be  tested 
should  be  allowed  to  stand  over  night,  covered  wtih  purified  carbon 
tetrachloride.     The  test  to  be  performed  in  subdued  light. 

(4)  The  cement  shall  not  flash  at  a  less  temperature  than  350 
degrees  F.,  New  York  State  Closed  Oil  Tester. 

Flux. 

Use  the  flux  specifications  prepared  by  the  Committee  on  Asphalt 
Pavement  Specifications. 


Coal  Tar  Cement. 

The  coal  tar  cement  shall  be  residue  of  the  distillation  of  coal 
tar  only,  and  shall  be  refined  for  the  special  purpose  of  making  a 
paving  cement. 

No  mixture  of  hard  pitch  with  the  lighter  oils  of  coal  tar  will  be 
permitted. 

Its  specific  gravity  shall  be  not  less  than  1.20  nor  more  than  1.29 
at  69  degrees  F. 

The  melting  point  determined  by  the  cube  method  shall  be  not 
less  than  100  degrees  F.,  and  not  more  than  115  degrees  F. 

It  shall  contain  not  less  than  15  per  cent,  nor  more  than  30  per 
cent  of  free  carbon  insoluble  in  benzol. 

It  shall  be  free  from  water  as  determined  by  distillation  and  shall 
show  upon  ignition  not  more  than  l/2  per  cent  of  inorganic  matter. 

No  distillate  shall  be  obtained  lower  than  338  degrees  F.,  and 
up  to  600  degrees  not  less  than  5  per  cent  and  not  more  than  20 
per  cent  of  distillate  shall  be  obtained.  The  distillate  shall  be  of 
a  gravity  of  not  less  than  1.03  at  60  degrees  F.  The  residue  shall 
have  a  melting  point  of  not  more  than  165  degrees  F.  In  making 
this  distillation  an  8-ounce  glass  retort  shall  be  used  and  the  ther- 
mometer suspended  so  that  before  applying  the  heat  the  bulb  of  the 
thermometer  is  one-half  inch  above  the  surface  of  the  liquid.  The 
melting  point  of  the  pitch  shall  be  determined  by  suspending  a 
l/2 -inch  cube  in  a  beaker  of  water  one  inch  above  the  bottom.  The 
temperature  shall  be  raised  9  degrees  per  minute  from  60  degrees  F. 
The  temperature  recorded  the  instant  the  pitch  touches  the  bottom 
shall  be  considered  the  melting  point  of  the  pitch.  In  testing  the 
original  materials  the  initial  temperature  shall  be  40  degrees  F. 

Water  Gas  Tar  Cement. 

1.  The  specific  gravity  at  25  degrees  C.  shall  be  between  1.155 
and   1.170. 

2.  On  extraction  with  cold  carbon  disulphide  at  room  tempera- 
ture for  20  minutes,  not  less  than  97^4  per  cent  shall  be  soluble. 

3.  When  tested  in  a  penetrometer  at  25  degrees  C.  with  a  No.  2 
needle  under  100  grams  load  for  5  seconds,  it  shall  have  a  penetra- 
tion of  not  less  than  27.5  m.m.  and  not  more  than  32.5  m.m. 

10 


4.  When  100  c.m.  are  distill  in  a  250  c.c.  Engler  flask  accord- 
ing to  the  method  proposed  by  the  American  Society  for  Testing 
Materials,  the  loss  by  weight  shall  be  within  the  following  limits: 

From  Start  to   170  degrees  C 0 

170  to  225  degrees  C not  over    y2% 

225  to  270  degrees  C from  2  to  6% 

270  to  300  degrees  C from  5  to  9% 

Residue.  .      not  less  than  84% 


SPECIFICATIONS  FOR  BITULITHIC  PAVEMENT  ON  ANY  APPROVED 
FORM  OF  FOUNDATION. 


Wearing  Surface. 

On  the  foundation  prepared  as  herein  above  specified,  shall  be 
laid  the  Bitulithic  Wearing  Surface  and  Seal  Coat,  described  below, 
so  as  to  have  a  thickness  of  two  (2)  inches  after  thoro  com- 
pression. The  Wearing  Surface  shall  be  composed  of  hard  crushed 
stone,  sand,  and  Bitulithic  Cement. 

The  Bitulithic  Cement  herein  specified  besides  being  produced 
under  the  direction,  processes,  supervision  and  laboratory  inspection 
of,  and  with  ingredients  approved  by  Warren  Brothers  Company, 
shall  in  all  respects  comply  with  the  specifications  for  Asphalt 
Cement  contained  in  the  sheet  Asphalt  Specifications  of  the  Ameri- 
can Society  of  Municipal  Improvements. 

Either  of  the  two  following  methods  and  apparatus  shall  be  used 
in  the  preparation  of  the  wearing  surface. 

1.  The  stone  and  sand  shall  be  heated  in  a  rotary  dryer  and 
while  still  hot  separated  into  the  desired  number  of  different  sizes 
by  means  of  a  rotary  screen  having  a  minimum  screen  opening  of 
about  1/10  of  an  inch  and  a  maximum  opening  of  about  1^2  inch. 
The  openings  in  the  successive  screen  sections  up  to  one-half  inch 
(5/2")  size,  shall  not  vary  more  than  one-fourth  of  an  inch  (}4") 
and  not  more  than  three  quarters  of  an  inch  (24")  for  the  sizes 
larger  than  one-half  inch  (^").  The  aggregate  thus  separated 
shall  pass  into  a  bin  having  sections  or  compartments  corresponding 
to  the  screen  sections.  From  these  compartments  the  aggregate  shall 

11 


pass  into  a  weigh  box,  resting  on  a  multi-beam  scale.  The  desired 
amount  of  aggregates  from  each  of  the  above  compartments,  shall  be 
accurately  weighed  separately  on  the  scale  and  the  batch  dropped 
into  a  "twin  pug"  mixer,  where  it  shall  be  intimately  associated  and 
thoroly  commingled  with  a  predetermined  quantity  of  Bitulithic 
Cement  sufficient  to  coat  all  particles  of  the  aggregate  and  to  fill 
the  voids  in  same. 

2.  The  stone  and  sand  shall  first  be  carefully  measured  as  to 
sizes  and  a  definite  quantity  of  each  size  shall  then  be  fed  into  an 
elevator  terminating  in  a  hopper  or  bin  which  discharges  into  a 
rotary  dryer  or  heater,  both  hopper  and  heater  being  so  designed 
as  to  keep  each  batch  by  itself  until  heated.  From  the  rotary  heater 
the  batch  of  mineral  aggregate  shall  pass  into  a  rotary  cylindrical 
mixer  containing  blades,  spirals  or  other  devices  for  producing  a 
uniform  mixture  of  the  mineral  aggregate  with  a  predetermined 
quantity  of  the  Bitulithic  Cement  sufficient  to  coat  all  the  particles 
of  the  aggregate  and  to  fill  the  voids  in  same. 

The  different  sized  particles  of  stone  and  sand  ranging  in  size 
from  impalpable  powder  to  about  one-half  the  thickness  of  the 
wearing  surface,  shall  be  combined  in  such  proportions  as  to  secure 
in  the  mineral  aggregate  density,  or  low  percentage  of  voids,  and 
inherent  stability  or  resistance  to  displacement,  producing  an  aggre- 
gate which  when  combined  with  the  Bitulithic  Cement  and  laid  in 
place  and  compacted  will  form  a  street  paving  structure  consisting 
of  mineral  aggregate  of  different  sizes  and  the  Bitulithic  Cement 
which  permeates  the  entire  mass,  fills  the  voids  and  unites  the 
various  particles  thereof.  If  the  crushed  stone  and  sand  do  not 
contain  enough  finely  divided  particles,  or  impalpable  powder  to 
produce  a  low  percentage  of  voids  in  the  aggregate,  the  deficiency 
shall  be  made  up  by  the  addition  of  any  other  suitable  fine  mineral 
matter. 

The  mixture  and  ingredients  thereof  shall  be  maintained  at  a 
temperature  consistent  with  good  workmanship.  The  mixture  when 
reaching  the  street  shall  be  hot  enough  to  allow  of  being  easily 
spread  and  raked  and  shall  not  be  so  hot  as  to  injure  the  Bitulithic 
Cement. 

Surface  Finish   or  Seal  Coat. 

There  shall  be  spread  over  the  Bitulithic  surface  mixture  a  seal 
coat,  using  per  square  yard  of  Bitulithic  pavement  approximately 
one-fourth  (/4)  gallon  of  Bitulithic  Cement,  into  which  shall  be 

12 


incorporated  approximately  twenty-five  (25)  pounds  of  mineral 
aggregate  not  larger  than  one-quarter  ( l/\. )  inch  diameter.  After 
spreading  the  seal  coat,  it  shall  be  thoroly  rolled  into  the  Bitulithic 
surface  mixture.  On  grades  a  coarser  aggregate  may  be  used. 

General. 

Each  layer  of  the  work  shall  be  kept  as  free  as  possible  from  dirt, 
so  that  it  will  unite  with  the  succeeding  layer. 

The  bituminous  composition  or  cement  shall  in  each  case  be  free 
from  water  and  shall  be  especially  refined  to  remove  volatile  and 
other  matter  susceptible  to  atmospheric  influences  . 

Warren  Brothers  Company,  owner  of  the  patents  used  in  the 
construction  of  the  Bitulithic  Pavement,  shall  file  with  the  proper 
official  or  board  which  is  about  to  receive  bids  for  the  work,  a 
properly  executed  binding  agreement  to  furnish  any  contractor 
desiring  to  bid  for  the  work  all  the  necessary  Bitulithic  Surface 
material,  mixed  ready  for  use,  and  Bitulithic  Cement,  and  the  sand, 
gravel,  or  stone  screenings  for  the  surface  finish  course,  in  accord- 
ance with  Sections,  "Wearing  Surface"  and  "Surface  Finish,"  at  a 
definite  reasonable  price  per  square  yard.  Said  price  shall  include 
a  license  to  use  all  of  the  patents  required  in  the  construction  of 
the  Bitulithic  Pavement  as  herein  specified. 

The   acceptance   of   bids   by 

and  the  letting  of  a  contract  for  the  same  shall  be  deemed  by 
Warren  Brothers  Company  to  be  an  acceptance  of  its  proposal  by 

and  by  the  Contractor  to  whom  such  contract  shall  be  awarded,  and 
are  all  that  shall  be  necessary  to  bind  Warren  Brothers  Company 
to  said  agreement.  The  filing  of  a  bid  under  these  specifications 
will  be  construed  as  an  acceptance  of  the  terms  of  the  license  agree- 
ment filed  by  the  Warren  Brothers  Company,  at  the  price  fixed  in 
said  agreement,  which  is  on  file  with  the  proper  official  or  board. 


Boston,  Mass.,  Nov.  27th,  1915. 
Mr.  Chas.  C.  Brown,  C.  E.,  Secretary, 

American   Society  of   Municipal   Improvements, 

Indianapolis,    Indiana. 
Dear  Sir: — 

In   accordance  with  our  verbal   statement  to   the   Sub-Committee 
on    Bituminous    Paving    Specifications,    the    General    Committee    on 

13 


Paving  Specifications,  and  subsequently  on  the  floor  of  the  Conven- 
tion of  the  Society  at  Dayton,  we  hereby  agree  that  a  pavement  con- 
structed by  the  use  of  the  proportions  of  mineral  aggregate  enumer- 
ated below,  combined  with  bituminous  cement,  will  not  possess  the 
inherent  stability  and  density  covered  by  the  claims  of  and,  therefore, 
will  not  infringe  on  our  patents.  The  proportions  referred  to  as 
adopted  by  the  Society  at  the  Dayton  convention  being  as  follows: 


Passing  200  mesh  screen 

80  mesh  screen 

40  mesh  screen 

20  mesh  screen 

8  mesh  screen 

4  mesh  screen 

2  mesh  screen 


Passing 
Passing 
Passing 
Passing 
Passing 
Passing 


7  to  10  per  cent. 
10  to  20  per  cent. 
10  to  25  per  cent. 
10  to  25  per  cent. 
10  to  20  per  cent. 
15  to  20  per  cent. 

5  to  10  per  cent. 


Very  truly  yours, 

-WARREN  BROTHERS  COMPANY, 
By  (Signed)  Geo.  C.  Warren, 

President. 


14 


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